Physiological responses of the early zoeal stages of Palaemon pandaliformis Stimpson and Palaemon northropi (Rankin) to salinity variation

The effect of salinity variation (0, 7, 14, 21, 28 and 35S) on survival, moulting and respiratory metabolism of the early zoeal stages of the shrimps Palaemon pandaliformis and P. northropi from the northern coast of the State of São Paulo, Brazil is investigated. Freshly hatched larvae were maintained at 20 °C, in each salinity for a maximum of seven days. Oxygen consumption measurements were made at 20 °C for each salinity using Cartesian diver microrespirometers. In 0S, all P. northropi zoeae died after 24 h while 24% of the P. pandaliformis zoeae survived until 4 days. Zoeae of both species survived poorly in 7S, the best survival for the two species (90%) being registered in 28%.S. Palaemon northropi zoeae did not survive 35S while 45% survival was recorded for P. pandaliformis zoeae in this medium after seven days. Moulting did not occur in zoeae of either species in 0%.S, nor in P. northropi in 7S. The metabolism-salinity curve for P. pandaliformis zoea I is very stable over the range 0–21S while that for P. northropi exhibits complete salinity independence from 21–35 S. Thus, while the early zoeal stages, at least, are conspecific, both developing in the same environment as part of the coastal zooplankton community, they clearly maintain distinct physiological characteristics. The data presented possibly reflect genetic adaptations to the adult biotope already manifested in the first zoeae.     

Survival, osmoregulation and oxygen consumption of YOY coastal largemouth bass,Micropterus salmoides (Lacepede) exposed to saline media

The effect of salinity on survival, osmoregulation and oxygen consumption was determined on coastal young-of-the-year (YOY) largemouth bassMicropterus salmoides by exposing them to saline media of 0, 4, 8, 12, and 16‰. The data indicated a decrease in survival with longer exposure time and increased salinity. There were no significant differences in plasma osmolality with increased salinity from 0 to 8‰ but osmolality was significantly greater at 12‰ than 0‰ and osmolality from 16‰ was greater than all other salinity treatments. No significant differences in hematocrits were detected between 0 and 12‰, but hematocrits in the 16‰ treatment were significantly reduced compared to all other treatments. YOYM. salmoides are good osmoregulators up to 8‰ but increased salinity caused measurable osmoregulatory dysfunction. Oxygen consumption rate increased significantly as salinity increased, suggesting that adaptation of this species to hypersaline media is in part accompanied by increased energy expenditure.     

Larval salinity tolerance of the South American salt-marsh crab, Neohelice (Chasmagnathus) granulata: physiological constraints to estuarine retention, export and reimmigration

The semiterrestrial crab Neohelice (=Chasmagnathus) granulata (Dana 1851) is a predominant species in brackish salt marshes, mangroves and estuaries. Its larvae are exported towards coastal marine waters. In order to estimate the limits of salinity tolerance constraining larval retention in estuarine habitats, we exposed in laboratory experiments freshly hatched zoeae to six different salinities (5–32‰). At 5‰, the larvae survived for a maximum of 2 weeks, reaching only exceptionally the second zoeal stage, while 38% survived to the megalopa stage at 10‰. Shortest development and negligible mortality occurred at all higher salt concentrations. These observations show that the larvae of N. granulata can tolerate a retention in the mesohaline reaches of estuaries, with a lower limit of ca. 10–15‰. Maximum survival at 25‰ suggests that polyhaline conditions rather than an export to oceanic waters are optimal for successful larval development of this species. In another experiment, we tested the capability of the last zoeal stage (IV) for reimmigration from coastal marine into brackish waters. Stepwise reductions of salinity during this stage allowed for moulting to the megalopa at 4–10‰. Although survival was at these conditions reduced and development delayed, these results suggest that already the zoea-IV stage is able to initiate the reimmigration into estuaries. After further salinity reduction, megalopae survived in this experiment for up to >3 weeks in freshwater, without moulting to juvenile crabs. In a similar experiment starting from the megalopa stage, successful metamorphosis occurred at 4–10‰, and juvenile growth continued in freshwater. Although these juvenile crabs showed significantly enhanced mortality and smaller carapace width compared to a seawater control, our results show that the late larval and early juvenile stages of N. granulata are well adapted for successful recruitment in brackish and even limnetic habitats.     

Influence of temperature and salinity on embryonic development ofParacentrotus lividus (Lmk, 1816)

The combined effects of temperature and salinity on early development of the sea urchinParacentrotus lividus (Lmk, 1816) are reported. The optimal temperature-salinity combinations for development are 18 °–20 °C and 34–35‰; there is a significant temperature-salinity interaction. The optimal conditions found in the experiments are above the mean yearly values for the sampled population's environment (North Adriatic Sea), being more similar to those of the Tyrrhenian Sea. These results suggest that embryonic tolerances to temperature and salinity are under genetic and not environmental control.     

Changes in protein profile and amino acids in <Emphasis Type="Italic">Cladophora vagabunda</Emphasis> (Chlorophyceae) in response to salinity stress

The aim of the present study was to detect organic substances functioning as osmoticants that are used by the intertidal alga, Cladophora vagabunda (L.) Hoek (Chlorophyceae), to adapt to a wide range of salinity. The major constituents of the amino acid pool were aspartate, glutamate, glycine, valine, lysine, histidine, arginine, and proline. There were concomitant increases in the acidic amino acids: aspartate and the glutamate and the basic amino acids: lysine, histidine and arginine in response to salinity stress. The appearance of proline at hypersalinity alone showed that it acts as an osmoticant. As salinity increased, there was a progressive shift in the electrophoretic pattern of protein bands. New peptide bands appeared under hyposalinity (10‰) and hypersalinity (65‰) stress conditions in addition to the usual bands which appeared in the control (35‰). Glycine betaine, which has been considered a novel organic osmolyte in a number of organisms, has also been observed in C. vagabunda in response to salinity stress. The synthesis of the compatible solute glycine betaine and the amino acid proline with increasing salinity illustrates the contention that marine algae establish an osmotic equilibrium primarily by the synthesis of organic compounds. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Influence of changes in sea water salinity on the growth,photosynthetic pigment content,and cell size of the benthic alga <Emphasis Type="Italic">Attheya ussurensis</Emphasis> Stonik,Orlova et Crawford, 2006 (Bacillariophyta)

The study deals with the effect of changes in salinity from 32 to 4‰ (at an interval of 4‰) on the growth, chlorophyll a and carotenoid contents, and cell size of the benthic alga Attheya ussurensis (Bacillariophyta). A. ussurensis showed high tolerance to reduced salinity and ability to adapt to salinity changes from 16 to 12‰. In this salinity range, the cells restored their shapes, sizes, and physiological functions. The number of cells and photosynthetic pigment content were highest at a salinity reduction to 24‰. At 8‰, algal cells remained alive, but the process of cell division was inhibited; as a result, the number of cells was significantly lower than in the control, the cells did not restore their sizes and shapes and remained deformed until the end of the experiment. A drop in salinity to 4‰ caused a complete loss of cell viability of A. ussurensis within a day of exposure to this factor.     

The Reaction of the Starfish Asterias amurensisand Patiria pectinifera (Asteroidea) from Vostok Bay (Sea of Japan) to a Salinity Decrease

The reactions of the starfish Asterias amurensis and Patiria pectinifera that live in Vostok Bay at the salinity of 32–33 to a salinity decrease were studied under laboratory conditions. The lower limits of the desalination tolerance range of A. amurensis and P. pectinifera were, respectively, 24 and 20. A. amurensis proved to be less resistant to desalination. Under experimental conditions, all specimens of this species survived the salinity of 22, while those of P. pectinifera tolerated 18. At the same time, A. amurensis responded more actively than P. pectinifera to unfavorable changes in the environment. Turned to their dorsal side and exposed to a salinity of 16 to 32, the former reverted to the normal position within a shorter time than the latter. Being a more euryhaline species, P. pectinifera endured a salinity decrease to 6 or 8 over, respectively, 21 or 28 h. However, only 30–40% of all specimens could recover locomotory activity 12 or 8.5 h after being placed into water of normal salinity.     

Halocafeteria seosinensis gen. et sp. nov. (Bicosoecida), a halophilic bacterivorous nanoflagellate isolated from a solar saltern

Recently, heterotrophic nanoflagellates (HNF) have been reported to actively ingest prokaryotes in high salinity waters. We report the isolation and culture of an HNF from a Korean saltern pond of 300‰ salinity. The organism is biflagellated with an acronematic anterior flagellum and never glides on surfaces. The mitochondria have tubular cristae. Neither transitional helix nor spiral fiber were observed in the transition zones of the flagella. The cell has a cytostome supported by an arc of eight microtubules, suggesting that our isolate is a bicosoecid. Our isolate had neither mastigonemes, lorica, body scales, nor cytopharynx and thus could not be placed in any of the presently described bicosoecid genera. Phylogenetic analysis of 18S rRNA gene sequences from stramenopiles confirmed the bicosoecid affinities of our isolate, but did not place it within any established genus or family. Its closest relatives include Caecitellus and Cafeteria. The optimal range of growth temperature was 30–35°C. The isolated HNF grew optimally at 150‰ salinity and tolerated up to 363‰ salinity, but it failed to grow below 75‰ salinity, indicating that it could be a borderline extreme halophile. On the basis of its morphological features and position in 18S rRNA trees we propose a novel genus for our isolate; Halocafeteria, n. gen. The species name Halocafeteria seosinensis sp. nov. is proposed.     

Effects of extreme changes of sea water temperature and salinity on the development of the sand dollar <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰, and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22° C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not settle during the experiment (14 days) at 14 ° C and in the absence of sand.     

Relationship Between Medium Salinity, Body Density, Buoyancy and Swimming in Artemia franciscana Larvae: Constraints on Water Column Use?

Body density measurements were carried out on larval Artemia franciscana that had been held for 24 h at either 33 or 100‰ after hatching. Body density was low (1.0308–1.0342 g ml⁻¹) by comparison with marine crustacean zooplankters or benthic freshwater crustaceans, and very stable, being only 0.3% higher in 100‰ than in 33‰. Vertical and horizontal swimming in 2nd instar larvae was studied at 8.5, 17, 34, 50, 100, 150 and 250‰ at 23 °C. At 8.5–50‰ downwards swimming was always significantly faster than upwards swimming, but in 100‰ downwards swimming was much slower than upwards swimming, indicating substantial positive buoyancy. At 150 and 250‰ downwards swimming was impossible. Horizontal swimming speed was unaffected by salinity over the range 8.5–100‰, but could not be studied at 150 and 250‰ as larvae could not leave the surface film. An asymptotic relationship between salinity and viscosity was found over the range 8.5–250‰. Calculations indicate a rise from 1.197 to 1.513 cp between 8.5 and 100‰, but this does not significantly impede horizontal locomotion. It appears that water column use by early stage Artemia larvae, that use a pair of 2nd antennae for rowing-type locomotion, is constrained by the increasing positive buoyancy associated with living at salinities above that corresponding to neutral buoyancy (approximately 48‰).     

Correlation of the distribution ofMesopodopsis slabberi (Crustacae,Mysidacea) with physico-chemical gradients in a partially-mixed estuary (Tamar,England)

The physical and chemical processes operating in the River Tamar Estuary (south-west England) have been comprehensively described and reported in the literature. There are well-established gradients of salinity, suspended sediment and oxygen which vary both on short-term (tidal) and long-term (seasonal) cycles. Freshwater runoff, the main factor determining salinity distribution, is also the cause of the high variability in suspended sediment concentrations. The biological processes are less well studied and information on the link between the benthic and pelagic systems is particularly lacking. Mysids, through their role as detritivores and as a major component in the diet of some fish, provide this link. Of the four species of mysid distributed longitudinally in the Tamar Estuary, the most abundant isMesopodopsis slabberi which occurs between 5 and 25 km from the estuary head. Observations over an annual cycle have shown marked seasonal changes in both abundance and distribution in the estuary. During winter and spring, densities remained generally low (<50 m⁻³) but, as water temperatures increased, the density increased and reachedca 1200 individuals m⁻³ in July. There was a shift in the longitudinal distribution ofM. slabberi in response to changes in the position of the salinity gradient. Adults comprised the majority of the population in salinities less than 10‰ whereas juveniles and immature animals were distributed over a wider area than the adults and occurred in water of higher salinity than the main adult distribution.M. slabberi appears to utilise the two-layered estuarine circulation to maintain its position in the estuary.     

Physiological responses of Pterocladia and Gelidium (Gelidiales,Rhodophyta) from the Azores,Portugal

Manometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosum from the Azores, Portugal to determine optimal values of temperature, light and salinity for growth. Physiological responses were considered in relation to vertical distribution patterns of these species commonly observed throughout the Azores. Optimal parameters for the growth of Pterocladia capillacea, Gelidium latifolium and G. spinulosum were 17 to 25 °C, a photon flux density between 200 and 300 µmol m^–2 s^–1 and salinities of 25 to 35.     

Saline acclimation of striped mojarra <Emphasis Type="Italic">Eugerres plumieri</Emphasis> (Cuvier 1830) and optimal dosage of carp pituitary extract (CPE) to induce spawning

The main objective of the current study was to determine an optimal dosage of commercial carp pituitary extract (CPE) of the conventional heteroplastic hypophysation technique to induce spawning in the wild caught striped mojarra broodstock Eugerres plumieri under laboratory conditions. We also describe trials testing saline acclimation regimes (changes from 10‰ to 30‰) prior to hormonal induction. For saline acclimation, three treatments were performed: first and second treatments began 1-day after conditioning of broodstock fish with a total duration of the saline changes lasting 1-day and 2-days, respectively. The third treatment began 30-days after conditioning with a 7-day saline regime. After reaching 30‰, all fish from the first and second treatments died after the fourth and ninth days, respectively; while the fishes in the third treatment survived more than two years. These fish remain on public exhibit in the “Mundo Marino” Aquarium, Santa Marta, Colombia. Four treatments of hormonal induction were tested on females using a total concentration of 5-mg of CPE per kg of body weight: first, second and third treatments were applied in two hormonal doses that corresponded to 10%–90%, 30%–70% and 40%–60%, respectively, with time intervals between doses of 14-h for the first and second treatment and of 12-h for the third treatment. The fourth treatment was applied in four hormonal doses that it corresponded to 20%–20%–30%–30% with 12-h time intervals between doses. Only the fishes of the fourth treatment resisted the induction, continued to live and reached spawning artificially. Water temperature remained at 28 ± 1°C and at 30‰ salinity during the study. The “dry” method of fertilization was used. The fertilized eggs were incubated at 30‰ and 35‰ salinities. These eggs reached the Morula early stage, but were later attacked by protozoan. These results suggest that fast changes of saline and limited hormonal dosages do not offer effective results in Eugerres plumieri. This work provided fundamental procedures for the culture and maintenance of live broodstock for striped mojarra in saltwater and/or coastal lagoon habitats and provides an effective and viable dosage of CPE for artificial spawning and commercial production in this species.     

Effects of salinity and cadmium interaction on reproduction and growth during three successive generations ofOphryotrocha labronica (polychaeta)

The long-term effects of different cadmium (0.2 and 0.4 ppm) and salinity levels (30, 25, and 20 ‰ S) on growth and egg-mass production ofOphryotrocha labronica (La Greca & Bacci) were investigated over three generations. Low salinity levels and the presence of cadmium resulted in reduced growth rates, prolonged times to reach sexual maturity, and reduced size at maturity. Three-way analysis of variance showed significant interaction effects of generation and cadmium for the different growth processes tested. Using response-surface methods, 0.2 ppm cadmium was shown to have a greater effect on growth rate at the third generation than the first and second generations at the three salinities tested. Increased effects were observed from first to second generation at 0.4 ppm cadmium and 30 and 25 ‰ S, whereas effects decreased from second to third generation. At 0.4 ppm cadmium and salinity of 20 ‰ the first generation was not able to produce viable larvae.     

Effects of temperature and salinity on embryonic development of turbot (Scophthalmus maximus L.) from the North Sea, and comparisons with Baltic populations

Optimum temperature and salinity conditions for viable hatch were studied for turbot (Scophthalmus maximus L.) from the North Sea. Temperatures ranging from 6 to 22°C and salinities from 5 to 35‰ were used. Optimum conditions were observed to be between 12 and 18°C at salinities between 20 and 35‰. This contrasted with corresponding data for turbot from the southern Baltic proper, according to which survival sharply decreased in temperatures below 14°C and was high in salinities of 10 to 15‰. Thus, it is concluded that Baltic and Atlantic turbot should be considered as different races.     

Effects of temperature and salinity on the growth of Gracilaria verrucosa and G. chorda, with the Potential for mariculture in Korea

Effects of temperature and salinity on the growth of the two agarophytes, Gracilaria verrucosa (Hudson) Papenfuss and Gracilaria chorda Holmes were examined in Korea. Both species grew over a wide range of temperatures (10–30 ^∘C) and salinities (5–35‰), and grew well at 17–30 ^∘C and a salinity of 15–30‰. In culture, G. verrucosa grew faster than G. chorda and their maximum growth rates were 4.95% day⁻¹ (30 ^∘C, 25‰) and 4.47% day⁻¹ (at 25 ^∘C, 25‰), respectively. In the field population the maximum growth and fertility of G. chorda were observed in summer. The growth rate of G. verrucosa was slightly higher than that of G. chorda for 2 weeks on the cultivation rope and in culture but it was much lower after being contaminated with epiphytes. The biomass of the epiphytes was 0.82 g dry wt. per host plant in G. verrucosa and 0.001 g in G. chorda. G. chorda exhibited resistance to epiphytism and grew 7 times in length and the dry weight increased 15 times after 55 days. In conclusion, G. chorda appears to be a good agarophyte with a fast growth rate and resistance to epiphytesm, and compared with G. verrucosa, has good potential for commercial cultivation.     

Influence of salinity on Na+ and K+ accumulation, and gas exchange in Avicennia germinans

We analysed plant growth, ion accumulation, leaf water relations, and gas exchange of Avicennia germinans (L.) L. subjected to a long-term, controlled salinity gradient from 0 to 55 ‰. Growth and leaf area were affected by salinity higher than 10 ‰. As salinity increased, the predawn leaf water potential (Ψ_w) and leaf osmotic potential (Ψ_s) decreased. Leaf Ψ_w was at least −0.32 MPa lower than the Ψ_w of solution. Na⁺ and K⁺ ions explained about 78 % of decrease in Ψ_s. K⁺ tissue water concentration decreased by more than 60 % in all salinity treatments as compared with those grown at 0 ‰. Inversely, Na⁺ concentration in tissue water increased with nutrient solution salinity. The maximum net photosynthetic rate (P _N) and stomatal conductance (g _s) decreased by 68 and 82 %, respectively, as salinity increased from 0 to 55 ‰; the intercellular CO₂ concentration (C _i) followed the same trend. The P _N as a function of C _i showed that both the initial linear slope and upper plateau of the P _N vs. C _i curve were markedly affected by high salinity (40 and 55 ‰).     

Salinity-stress-induced changes in the resistance of embryos of the White Sea herringClupea pallasi marisalbi to freshwater

The short-term effects of extremely low salinity (3‰) on the resistance of White Sea herring to freshwater were studied. An increasing resistance of the embryos against a sudden drop in salinity, and a decreasing resistance against gradual changes in salinity (to 0‰) was revealed.     

Spawning and early ontogenesis of the littoral polychaete <Emphasis Type="Italic">Namanereis littoralis</Emphasis> (Grube, 1876) (Nereididae,Namanereidinae)

For the first time, under laboratory conditions, development of the polychaete Namanereis littoralis (Grube, 1876) is investigated. Under conditions of the Sea of Japan, its reproduction occurs in July and is confined to the season of monsoon rains. Fertilization is external. Spawning manifests no epitocous transformations. Fecundity is low, ovicells are rich in yolk, and development is nonpelagic, lecithotrophic, embryonized, characterized by a high rate—5–8 days—and occurs in mucous clutches up to hatching of benthic juveniles. Temperature and salinity optima of development are 22–27°C and 16–21‰, respectively, characterizing the species as subtropical brackish-water by its origin. Archaic and specialized traits are noted in the early ontogenesis of N. littoralis.